1. Field of Invention
The present invention relates generally to a semiconductor substrate processing system. More specifically, the invention relates to a method and apparatus for polishing a semiconductor substrate.
2. Description of the Background Art
In semiconductor substrate processing, the transfer of substrates between modules is required to optimize processing rates while minimizing risk of substrate damage and contamination. The typical method of transferring a substrate between processing and support equipment is to move the substrate using a paddle manipulated by a robot. In most instances, the substrate is lifted from a pedestal using pins to allow the paddle to be positioned under the center portion of the substrate. In other modules, such as transfer cassettes, the substrate is supported horizontally at the edges, allowing the paddle access under the substrate. The paddle is then lifted to engage the substrate and carry the substrate from one module or station to another. Often, the paddle is equipped with a mechanism that secures the substrate to the paddle during transfer and releases the substrate once the desired destination is reached. Such a mechanism may be a vacuum device, an electrostatic chuck, a substrate edge gripping mechanism and the like.
The traditional, horizontal paddle and retention mechanisms, while functional for passing substrates among certain semiconductor processing stages, are cumbersome when directed for use between certain types of semiconductor processing stages. The transfer between a factory interface and a polisher on Chemical Mechanical Polishing (CMP) system is an example of an area where the horizontal orientation of the substrate during transfer is not efficient.
The polisher generally removes the surface roughness of a substrate orientated horizontally with the assistance of a slurry. After polishing the substrate, some of the slurry remains on the substrate. If the slurry dries and hardens on the substrate surface, the substrate may become damaged, defective or unfit for further processing. Therefore, the polished substrates are normally cleaned by spraying the substrates with a cleaning fluid, scrubbing the substrates, and by using megasonics. The substrates can be cleaned either in a horizontal or vertical position. Those substrates cleaned vertically benefit from the assistance of gravity in removing the slurry and other contaminants from the substrate.
The 90 degrees difference in substrate orientation between the polishing and cleaning processes leads to a number of problems for a system builder and operator when using a traditional horizontally orientated substrate transfer mechanism. One problem is that a larger machine foot-print is required to accommodate rinsing a substrate while the substrate is horizontal, added stations for orientating the substrates and/or increased transfer distances. Additionally, the extra steps in substrate handling increases the probability of costly substrate damage and contamination.
Therefore, there is a need in the art for apparatus which facilitates substrate transfer between modules of a semiconductor processing system, wherein vertical orientation of the substrate is used during substrate transfer.
The disadvantages associated with the prior art are overcome by the present invention of a semiconductor substrate polishing method and system. More specifically, the substrate polishing system includes an input module and one or more polishing modules that have a transfer station. A first robot is disposed proximate the input module. The first robot has a first gripper that is rotatable on a first horizontal axis and is adapted to selectively pick and place the substrate vertically in the input module. A second robot is disposed proximate the input module and the polishing modules. The second robot has a second gripper that is rotatable on a second horizontal axis and is adapted to selectively pick and place the substrate vertically in the input module.
In another embodiment, the semiconductor substrate polishing system includes one or more chemical mechanical polishing modules, a factory interface module and a cleaning module having an input module at a first end. The cleaning module is disposed between the factory interface module and the one or more chemical mechanical polishing modules. A first robot has a first gripper that is disposed in the factory interface module and adapted to transfer substrates between the factory interface module, the input module and a second end of the cleaning module. A second robot is disposed proximate the input module and one or more polishing modules. The second robot has a second gripper that is adapted to transfer substrates between the input module, the first end of the cleaner and the one or more chemical mechanical polishing modules.
In another aspect, a method for transferring a semiconductor substrate is disclosed comprising the steps of providing the horizontally orientated semiconductor substrate at a first location; gripping the horizontally orientated semiconductor substrate with a first robot; moving the semiconductor substrate while changing the orientation of the semiconductor substrate from horizontal to vertical; releasing the vertical semiconductor substrate from the first robot into an input module, the input module maintaining the vertical orientation of the semiconductor substrate; gripping the vertical semiconductor substrate with a second robot; moving the semiconductor substrate while changing the orientation of the semiconductor substrate from vertical to horizontal; placing the horizontal semiconductor substrate at a second location and releasing the semiconductor substrate from the second robot.